1. School of Highway, Chang’an Univ., Xi’an 710064, China.
2. School of Highway, Chang’an Univ., Xi’an 710064, China (corresponding author).
3. CCCC First Highway Consultants Ltd., Xi’an 710075, China.
4. School of Civil Engineering, LanZhou Univ. of Technology, LanZhou 730050, China.
5. School of Civil Engineering, Chang’an Univ., Xi’an 710064, China.